Comparative analysis of the Pocillopora damicornis genome highlights role of immune system in coral evolution

Comparative analysis of the expanding genomic resources for scleractinian corals may provide insights into the evolution of these organisms, with implications for their continued persistence under global climate change. Here, we sequenced and annotated the genome of Pocillopora damicornis, one of the most abundant and widespread corals in the world. We compared this genome, based on protein-coding gene orthology, with other publicly available coral genomes (Cnidaria, Anthozoa, Scleractinia), as well as genomes from other anthozoan groups (Actiniaria, Corallimorpharia), and two basal metazoan outgroup phlya (Porifera, Ctenophora). We found that 46.6% of P. damicornis genes had orthologs in all other scleractinians, defining a coral ‘core’ genome enriched in basic housekeeping functions. Of these core genes, 3.7% were unique to scleractinians and were enriched in immune functionality, suggesting an important role of the immune system in coral evolution. Genes occurring only in P. damicornis were enriched in cellular signaling and stress response pathways, and we found similar immune-related gene family expansions in each coral species, indicating that immune system diversification may be a prominent feature of scleractinian coral evolution at multiple taxonomic levels. Diversification of the immune gene repertoire may underlie scleractinian adaptations to symbiosis, pathogen interactions, and environmental stress.

Dynamic regulation of partner abundance mediates response of reef coral symbioses to environmental change

Regulating partner abunclance may allow symmotic organisms to mediate interaction outcomes, facilitating adaptive responses to environmental change. To explore the capacity for-adaptive regulation in an ecologically important endosymbiosis, we studied the population dynamics of symbiotic algae in reef-building corals under different abiotic contexts. We found high natural variability in symbiont abundance in corals across reefs, but this variability converged to different symbiont-specific abundances when colonies were maintained under constant conditions. When conditions changed seasonally, symbiont abundance readjusted to new equilibria. We explain these patterns using an a priori model of symbiotic costs and benefits to the coral host, which shows that the observed changes in symbiont abundance are consistent with the maximization of interaction benefit under different environmental conditions. These results indicate that, while regulating symbiont abundance helps hosts sustain maximum benefit in a dynamic environment, spatiotemporal variation in abiotic factors creates a broad range of symbiont abundances (and interaction outcomes) among corals that may account for observed natural variability in performance (e.g., growth rate) and stress tolerance (e.g., bleaching susceptibility). This cost or benefit framework provides a new perspective on the dynamic regulation of reef coral symbioses and illustrates that the dependence of interaction outcomes on biotic and abiotic contexts may be important in understanding how diverse mutualisms respond to environmental change.

Predilection of hemolytic anemia-associated leg ulcers for the medial malleolus

BACKGROUND

Ischemic ulcers are usually found above the lateral, and venous stasis ulcers at the medial malleoli. Leg ulcers occur in at least 25% of sickle cell disease (SSD) patients in clinic populations, usually in the malleolar region. The function of the large leg veins in most SSD patients is unimpaired.

PATIENTS AND METHODS

We determined leg ulcer location in 41 sickle cell anemia (SS), and 4 sickle-beta 0 thalassemic patients with longstanding chronic and/or recurrent leg ulceration, and reviewed published reports of leg ulcers in hereditary spherocytosis and thalassemias.

RESULTS

Of the 57 legs of the 45 SSD patients with only 1 ulcer, 42 (74%) were medial and 15 lateral. The difference was significant (p < 0.001). Of patients with only a single ulcer, 22 were medial and 4 lateral. Of 15 reported patients with leg ulcers related to spherocytosis or thalassemia, 20/24 (83%) ulcers were medial.

CONCLUSIONS

The medial malleoli are the most common site of leg ulceration in SSD and in other chronic hemolytic anemias. This suggests that stasis may play a role in the leg ulceration associated with chronic hemolytic anemia.

Impaired venous hemodynamics in a minority of patients with chronic leg ulcers due to sickle cell anemia

BACKGROUND

Chronic or recurrent leg ulceration occurs in 25% of sickle cell anemia patients, but not in the remaining 75%. Doppler studies of venous function were normal in 16 sickle cell anemia patients with leg ulcers.

PATIENTS AND METHODS

Venous Duplex Ultrasound was used to study 33 sickle cell anemia patients with chronic leg ulcers.

RESULTS

Six of the 33 patients had venous reflux in at least one leg.

CONCLUSIONS

Venous insufficiency may contribute to the development of leg ulcers in a minority of sickle cell anemia patients. A minority of sickle cell anemia patients with chronic leg ulcers can be shown to have leg venous reflux by duplex ultrasound imaging.

Significant complications can occur with ischemic heart disease and tilt table testing

We present an elderly patient who had syncope, with known coronary artery disease and a conduction abnormality. Because of a possible vasovagal reaction, the patient underwent a tilt table test prior to evaluation of ischemia or her LV function. During the tilt table test on isoproterenol, the patient developed ventricular fibrillation which was corrected immediately by cardioversion. Subsequently, the patient was found to have significant coronary artery disease which was treated with stenting and angioplasty. After treatment, there were no inducible arrhythmias on full dose isoproterenol. This case reports a significant complication that may occur when tilt table testing with isoproterenol and ischemia.

Catheter ablation of accessory pathways, atrioventricular nodal reentrant tachycardia, and the atrioventricular junction: final results of a prospective, multicenter clinical trial. The Atakr Multicenter Investigators Group

BACKGROUND

The purpose of this study was to evaluate the safety and efficacy of a temperature-controlled radiofrequency catheter ablation system.

METHODS AND RESULTS

The patient population included 1050 patients who had undergone ablation of atrioventricular nodal reentrant tachycardia (AVNRT), an accessory pathway (AP), or the atrioventricular junction (AVJ). Ablation was successful in 996 patients. The probability of success was highest among patients who had undergone ablation of the AVJ, lowest in patients who had undergone ablation of an AP, and in between for patients who had undergone ablation of AVNRT. A major complication occurred in 32 patients. Four variables predicted ablation success (AVJ, AVNRT, or left free wall AP ablation and an experienced center). Four factors predicted arrhythmia recurrence (right free wall, posteroseptal, septal, and multiple APs). Two variables predicted development of a complication (structural heart disease and the presence of multiple targets), and 3 variables predicted an increased risk of death (heart disease, lower ejection fraction, and AVJ ablation).

CONCLUSIONS

These findings may serve as a guide to clinicians considering therapeutic options in patients who are candidates for ablation.

Early results of AV sequential pacing on left ventricular outflow obstruction after Senning procedure

Dual chamber pacing was shown to decrease left ventricular outflow tract (LVOT) obstruction in patients with hypertrophic cardiomyopathy 30 years ago. We report early results of AV sequential pacing from the LV apex in a patient with transposition of the great arteries who is post-Senning procedure. LVOT obstruction resulted from septal deviation and systolic anterior motion of the mitral valve. Pacing was indicated for sinus node dysfunction. AV sequential pacing with a short optimal AV interval of 60 ms demonstrated a 45% reduction in the degree of LVOT obstruction. This article suggests that LVOT obstruction after the Senning procedure can be palliated by asynchronous septal contraction induced by AV sequential pacing, even if the activation is from LV apex, and avoid or postpone surgery in selected situations.

Predictors of fluoroscopy time and estimated radiation exposure during radiofrequency catheter ablation procedures

The objective of this study was to identify factors that predict fluoroscopy duration and radiation exposure during catheter ablation procedures. The patient population included 859 patients who participated in the Atakr Ablation System clinical trial at 1 of 9 centers (398 male and 461 female patients, aged 36 +/- 21 years). Each patient underwent catheter ablation of an accessory pathway, the atrioventricular junction, or atrioventricular nodal reentrant tachycardia using standard techniques. The duration of fluoroscopy was 53 +/- 50 minutes. Factors identified as independent predictors of fluoroscopy duration included patient age and sex, the success or failure of the ablation procedure, and the institution at which the ablation was performed. Catheter ablation in adults required longer fluoroscopy exposure than it did in children. Men required longer durations of fluoroscopy exposure than did women. The mean estimated "entrance" radiation dose was 1.3 +/- 1.3 Sv. The dose needed to cause radiation skin injury was exceeded during 22% of procedures. The overall mean effective absorbed dose from catheter ablation procedures was 0.025 Sv for female patients and 0.017 Sv for male patients. This degree of radiation exposure would result in an estimated 1,400 excess fatal malignancies in female patients and 2,600 excess fatal malignancies in male patients per 1 million patients.

The initial assessment of the HIV-infected patient

The initial assessment of the patient with HIV disease requires clinical staging, identification of HIV-related and nonrelated illness, discussion of specific psychosocial issues, initiation of the process of patient education, and initiation of a sustained partnership between patient and clinician. The clinical content of the assessment depends on knowledgeable history-taking, focused physical examination, and specific laboratory tests. Partnering increases the likelihood of early recognition of important signs and symptoms and the institution of appropriate therapeutic measures. Successful and satisfying clinician-patient relationships help produce better patient outcomes.

Recurrence of conduction following radiofrequency catheter ablation procedures: relationship to ablation target and electrode temperature. The Atakr Multicenter Investigators Group

INTRODUCTION

More than 1 in 10 patients may develop recurrence of conduction after undergoing a successful radiofrequency catheter ablation procedure. The physiologic basis for recurrence following successful ablation procedures remains uncertain. The purpose of this study was to evaluate the role of electrode temperature as a predictor of recurrence following radiofrequency catheter ablation procedures.

METHODS AND RESULTS

The subjects of this study were 538 patients who underwent a successful attempt at radiofrequency catheter ablation of AV nodal reentrant tachycardia, an accessory pathway, and/or the AV junction. Patients were followed for a mean of 215 +/- 138 days. Conduction recurred in 35 (6.5%) of the 538 patients. Recurrence of conduction occurred in 25 (9.3%) of 270 patients undergoing ablation of an accessory pathway, 7 (3.5%) of 201 patients undergoing ablation of AV nodal reentrant tachycardia, and in 3 (4.5%) of 67 patients undergoing ablation of the AV junction. The electrode temperature achieved at successful sites associated with recurrence was not different from the temperature achieved at successful sites without recurrence (61.1 +/- 8.9 vs 61.6 +/- 9.1; P = 0.8). The likelihood of developing a recurrence was higher following ablation of accessory pathways than following ablation of AV nodal reentrant tachycardia or the AV junction (P = 0.03). Patients experiencing a recurrence following ablation of an accessory pathway had longer procedure durations (P = 0.0001). Ablation of left free-wall pathways was associated with a lower incidence of recurrence as compared with all other locations (P = 0.008).

CONCLUSION

The results of this study suggest that electrode temperature at the successful ablation site cannot be used to identify patients at highest risk of recurrence.

Gender and haplotype effects upon hematological manifestations of adult sickle cell anemia

In Africa, the beta-globin gene cluster haplotype may be associated with variation of Hb F levels in subjects with sickle cell anemia (SS). These observations have not yet been conclusively confirmed in SS out of Africa, perhaps because of small sample sizes, the predominance of haplotype heterozygotes, and diverse influences, including gender, upon Hb F levels. We studied 384 adult African-American SS patients (mean age, 31 years) and explored the relationship of gender, beta-globin gene cluster haplotype, and alpha thalassemia to hematological values and Hb F levels. Both haplotype and gender influenced Hb F concentration. In the total sample, Hb F was higher in females than in males (8.2 vs. 6.5%). In 35 males who were either homozygous for the Senegal chromosome or had the Senegal/Benin haplotype, the mean percent Hb F (8.0%) was equivalent to the Hb F level in females with Benin and Bantu haplotypes (approximately 7.5%). Both females and males homozygous for the Senegal haplotype chromosome or with the Senegal/Benin combination had a significant increase in Hb F compared to other groups. In 44 Senegal/Senegal or Senegal/Benin females the Hb F was 10.9%, or 1.0 g/dl, the highest value observed in all primary analysis groups. Preliminary analyses suggested that the presence of a Bantu chromosome blunted the gender-associated difference in Hb F, but Hb F differences between females with the Senegal/Benin haplotype (11.2%) and the Senegal/Bantu haplotype (8.8%) were not statistically significant. Hemoglobin concentrations were higher in males than in females except in subjects with at least one Senegal haplotype chromosome, where hemoglobin levels were equal. As expected, alpha thalassemia reduced the MCV, increased hemoglobin concentration, and lowered reticulocyte counts, regardless of haplotype. Hb F levels were not affected by the presence of alpha thalassemia in any group. We conclude that gender and beta-globin gene cluster haplotype interact significantly in the modulation of Hb F and anemia in adults with SS.

Temperature monitoring during radiofrequency catheter ablation procedures using closed loop control. Atakr Multicenter Investigators Group

BACKGROUND

The purpose of this study was to evaluate electrode temperatures obtained using a radiofrequency ablation system that incorporates closed loop feedback control to achieve preset target electrode temperatures and to determine if closed loop temperature control results in a lower incidence of developing a coagulum.

METHODS AND RESULTS

Two hundred seventy patients underwent catheter ablation of atrioventricular nodal reentrant tachycardia, an accessory pathway, and/or the atrioventricular junction using an ablation system incorporating closed loop feedback control. Forty-five patients underwent catheter ablation in the power control mode in which power output was fixed, and 225 patients underwent catheter ablation in the temperature control mode. A coagulum occurred during 0.8% of radiofrequency applications in the temperature control mode versus 2.2% in the power control mode (P < .01). Electrode temperatures were within 10 degrees C of the targeted temperature during 35% of applications in the temperature control mode. Ability to achieve the targeted electrode temperature was related to the target, with radiofrequency energy applications at the atrioventricular junction resulting in the highest temperatures (70 +/- 12 degrees C) and those for ablation of the atrioventricular node the lowest (59 +/- 11 degrees C, P < .001), using a maximum of 50 W of power for both. Electrode temperatures were higher during ablation of left free wall and posteroseptal pathways than during ablation of right free wall and septal pathways. The mean and minimum temperatures associated with success were 64 +/- 12 degrees C and 44 degrees C, respectively. Overall, the electrode temperatures at successful and unsuccessful ablation sites did not differ (P > .05).

CONCLUSIONS

Temperature monitoring with closed loop control of power output facilitates radiofrequency catheter ablation procedures by minimizing the probability of developing a coagulum while ensuring maximum lesion formation.

The acute chest syndrome in sickle cell disease: incidence and risk factors. The Cooperative Study of Sickle Cell Disease

The acute chest syndrome (ACS), a pneumonia-like illness in sickle cell patients, is one of the most frequent causes of their morbidity and hospitalizations. Repeated ACS events may predict the development of chronic lung disease. ACS is reported as a frequent cause of death in these patients. We examine here the incidence and risk factors of ACS in 3,751 patients with sickle cell disease who were observed prospectively for at least 2 years (19,867 patient-years [pt-yrs]) as part of a multicenter national study group. The ACS, defined by a new pulmonary infiltrate on x-ray, occurred at least once in 1,085 patients (2,100 events). ACS incidence was higher in patients with homozygous sickle cell disease (SS; 12.8/100 pt-yrs) and in patients with sickle cell-beta(0) -thalassemic (9.4/100 pt-yrs), and lower in patients with hemoglobin (Hb) SC disease (5.2/100 pt-yrs) and patients with sickle cell-beta(+) thalassemia (3.9/100 pt-yrs). alpha-Thalassemia did not affect the rate of ACS incidence in SS patients. Within each Hb type the incidence was strongly but inversely related to age, being highest in children 2 to 4 years of age (25.3/100 pt-yrs in SS) and decreasing gradually to its lowest value in adults (8.8/100 pt-yrs in SS). In SS children (< 10 years of age), we documented an age-related within-person reduction in ACS attack rates. Adults with a higher ACS rate had a higher rate of mortality (from all causes) than those with low ACS rates. This increased rate of mortality might also have contributed to the decline in ACS rate with age. In multivariate analysis, other factors affecting incidence in SS patients were degree of anemia (lower ACS rates in patients with lower steady-state Hb levels) and fetal Hb (lower rates in patients with high fetal Hb). There was also a positive association between ACS rate and steady-state leukocyte count. The relationship of ACS rate to higher steady-state Hb levels in SS patients is unexplained but might be caused by increased blood viscosity.

Chronotropic incompetence: a common and progressive finding in pacemaker patients

Thirty-eight patients (ages 40 to 77 years, mean 63) followed in a pacemaker clinic underwent exercise treadmill tests to determine chronotropic incompetence. There were 28 men and 10 women. Twenty-seven patients had atrioventricular (AV) block and 11 patients had sick sinus syndrome. All patients were exercised to fatigue. None of the patients were receiving beta-blockers or other drugs that could reduce heart rate. Maximum heart rate (MHR) and percent predicted maximum heart rate (% PMHR) were used as an index of chronotropic incompetence. Chronotropic incompetence was defined as inability to achieve a % PMHR of greater than 80%. The overall incidence of chronotropic incompetence was 58% (22 of 38 patients). We examined the relationship between chronotropic incompetence and the time to pacemaker implantation. We found that in patients who had pacemakers for less than 2 years, the mean MHR was 125 +/- 21.6 beats/min compared with 111.9 +/- 23.6 beats/min for patients who had pacemakers implanted for longer than 4 years. Similarly, the mean % PMHR decreased from 76.5 +/- 12.5% to 68.7 +/- 15.4% in patients with pacemakers less than 2 years versus those with pacemakers for more than 4 years. Fifty-three percent of the patients with a pacemaker less than 2 years old were chronotropic incompetent versus 70% of the patients with a pacemaker more than 4 years old. These data suggest that chronotropic incompetence worsens with time after pacemaker implant. To further support this, eight patients with AV block underwent a second stress test an average of 2 years following the first.(ABSTRACT TRUNCATED AT 250 WORDS)

Single- versus dual-chamber sensor-driven pacing: comparison of cardiac outputs

Previous studies have shown that single-chamber sensor-driven pacing improves exercise tolerance for patients with chronotropic incompetence. However, long-term single-chamber pacing has a number of inherent problems that limit its usefulness. Although sensor-driven dual-chamber pacing largely obviates the problems inherent with single-chamber sensor-driven pacing, the physiologic benefit of dual-chamber sensor-driven pacing has not yet been demonstrated. Accordingly, the purpose of this study was to compare exercise-induced cardiac output for patients with chronotropic incompetence, after programming their pacemakers to either a simulated sensor-driven single or simulated dual-chamber mode. Cardiac output was measured noninvasively at rest and peak exercise using standard Doppler-derived measurements, obtained in a blinded fashion. At rest the Doppler-derived resting VVI and DDD cardiac outputs were 4.49 +/- 0.3 L/min and 4.68 +/- 0.3 L/min, respectively. At peak exercise, the DDD cardiac output was 5.07 +/- 0.5 L/min, whereas the simulated activity VVI and DDD cardiac outputs were 6.33 +/- 0.6 L/min and 7.41 +/- 0.70 L/min, respectively. Analysis of variance showed that there was an overall significant difference in cardiac output from rest to peak exercise (p less than 0.001). However, only the simulated activity DDD cardiac output was significantly different from its respective control value (p less than 0.05). Thus this study shows for the first time that the addition of rate responsiveness to dual-chamber pacing results in a significant improvement in cardiac output for patients with chronotropic incompetence.

Effect of beta-globin gene cluster haplotype on the hematological and clinical features of sickle cell anemia

In 113 black American adults with sickle cell anemia (HbSS), we examined nine polymorphic restriction sites, including the Xmnl site 5' to the G gamma gene, to see whether haplotype is related to the level of HbF and the proportion of G gamma chains or if it influences the hematological and clinical features of the disease. Seventy-five percent of the patients were homozygous or heterozygous for the Benin (no. 19) or Central African Republic (Bantu, no. 20) haplotypes; 13.3% were homozygous or heterozygous for the Senegal (no. 3) haplotype, while 11.5% had other genotypes. Of the subjects, 14.2% were either homozygous or heterozygous for the Xmnl restriction site 5' to the G gamma gene. We found no effect of haplotype on HbF levels. The level of G gamma chains was 60.5% +/- 17.0% in individuals heterozygous or homozygous for haplotype no. 3 and was 46.9% +/- 11.6% in individuals with other haplotypes. Subjects with the Xmnl site 5' to the G gamma gene had G gamma globin levels of 59.5% +/- 16.7% while those lacking that site had an average of 47.2% +/- 12.1%. There were no significant differences among these groups in hemoglobin concentration, packed cell volume, mean cell volume, or clinical indicators of vaso-occlusive severity, including crises, hospitalizations per year, aseptic bone necrosis, acute chest syndrome, or leg ulcers. While the presence of haplotype 3 and the 5' G gamma Xmnl site were associated with increased G gamma chains, there was no effect on HbF level or other hematological and clinical features that might reflect disease severity. It is likely that determinants unrelated to haplotype, linked or unlinked to the beta-globin gene cluster, are the major effectors of differences in the levels of HbF in American patients with sickle cell anemia.

Overdose of cyclobenzaprine, the tricyclic muscle relaxant

A case of cyclobenzaprine (Flexeril) overdose in a 31-year-old woman is presented. The treatment rendered was analogous to treatment protocols implemented for tricyclic overdose. A review of the pharmacology of cyclobenzaprine, as well as the management of patients who overdose on this drug, is presented.

The leftward deletion alpha-thal-2 haplotype in a black subject with hemoglobin SS

We have identified a black individual with homozygous sickle cell anemia who is the silent carrier of alpha-thalassemia (genotype - alpha/alpha alpha) due to heterozygosity for the leftward deletion alpha-thal-2 haplotype. This deletion has not been described previously in a black subject and is the only leftward deletion that we have found among 255 alpha-thal-2 chromosomes from sickle cell subjects. Its effects on the clinical, hematologic, biosynthetic, and cellular pathology of sickle cell anemia resemble those reported for the common alpha-thalassemia genotypes of the black population.

Critical analysis of sensors for physiological responsive pacing

Physiological responsive pacing includes the application of sensors to measure physiologic variables, which in turn are used to control pacemaker rate. Six such systems are evaluated based on a comparison of (1) speed of response, (2) sensor reliability, and (3) system specificity. Although there is not a clear-cut solution, and every system has some weaknesses, several sensors seem more feasible than others. Much research remains to be done, and the indications and patient benefits must be established.

The effects of alpha-thalassaemia in HbSC disease

In HbSC disease, as in sickle cell anaemia, there is a spectrum of clinical severity. A reduced mean corpuscular volume and haemoglobin concentration, traits typical of thalassaemia, might retard sickling. We therefore ascertained the prevalence of alpha-thalassaemia in 53 adults with HbSC disease and related alpha-globin gene deletion to the haematologic and clinical findings. Alpha-globin genotype was identified by restriction endonuclease gene mapping. Indirect ophthalmoscopy and fluorescein angiography were used to document the presence of proliferative retinopathy. Bone necrosis and infarction were determined roentgenographically or by radionuclide scanning. Either heterozygous or homozygous alpha-thalassaemia-2 was present in 26% of patients. There was no relationship between alpha-globin genotype and haematocrit, pain crises, bone lesions, proliferation retinopathy or clinical severity score.

Oral propranolol treatment in infants and children

To determine the effectiveness of oral propranolol in children, we administered 0.5 to 4.0 mg/kg/day of the drug to 64 children (age one day to 20 years); 41 with cardiac dysrhythmias, six with isiopathic hypertrophic subaortic stenosis, and 17 with paroxysmal hypoxemic spells associated with right ventricular infundibular obstruction. A new liquid form of propranolol (10 mg/ml) was administered to 37 of the younger patients, and tablets were given to the other 27. Propranolol improved the dysrhythmia in 31 of 41 patients, being notably effective in supraventricular tachycardia and ventricular tachycardia associated with a prolonged QT interval. The drug also eliminated symptoms attributed to IHSS in six of six patients and abolished hypoxemic spells in 12 of 17. The liquid and tablets were equally effective; and the liquid had the advantage of allowing for accurate dose changes in younger children. We conclude that oral propranolol is an excellent drug for use in pediatric patients with certain types of cardiac disease.